Optical film, film article, surface light source device, and display device

Abstract

This optical film comprises a first surface and a second surface which face each other in a first direction. The optical film comprises a base material, an optical functional layer, and a surface layer in order from the second surface to the first surface. The optical functional layer includes light absorption parts and light transmission parts. The light absorption parts and the light transmission parts are alternately arranged along a second direction orthogonal to the first direction. The optical film has resistance to a bending resistance test by a method using a 12-mm-diameter cylindrical mandrel.

Description

Optical Film, Film Article, Surface Light Source Device, and Display Device

[0001] The present disclosure relates to an optical film, a film article, a surface light source device, and a display device.

[0002] Patent Document 1 discloses a louver film as an optical film. The louver film includes an optical function layer in which light absorption portions and light transmission portions are alternately arranged. The louver film is cut out from a long optical film (film article) including the optical function layer.

[0003] When cutting out from the long optical film, cracks may occur in the cut-out louver film. In particular, when the area ratio of the light absorption portion is increased, cracks are likely to occur at the boundary between the light absorption portion and the light transmission portion.

[0004] Japanese Patent Application Laid-Open No. 2017-45060

[0005] An object of the present disclosure is to suppress the occurrence of cracks in an optical film.

[0006] An optical film according to an embodiment of the present disclosure is an optical film including a first surface and a second surface facing each other in a first direction, including a base material, an optical function layer, and a surface layer in this order from the second surface toward the first surface, the optical function layer including a light absorption portion and a light transmission portion, the light absorption portion and the light transmission portion being alternately arranged along a second direction orthogonal to the first direction, and having resistance to a bending resistance test by a cylindrical mandrel method with a diameter of 12 mm.

[0007] According to the present disclosure, the occurrence of cracks in the optical film can be suppressed.

[0008] Figure 1 is a diagram illustrating one embodiment and is a cross-sectional view showing an example of an optical film. Figure 2 is an enlarged cross-sectional view of the optical film shown in Figure 1. Figure 3A is a graph showing an example of a load displacement curve obtained by the nanoindentation method. Figure 3B is a cross-sectional view illustrating a bending resistance test using the cylindrical mandrel method. Figure 4A is a diagram illustrating an example of a method for manufacturing the optical film shown in Figure 1. Figure 4B is a diagram illustrating an example of a method for manufacturing the optical film shown in Figure 1. Figure 4C is a diagram illustrating an example of a method for manufacturing the optical film shown in Figure 1. Figure 4D is a diagram illustrating an example of a method for manufacturing the optical film shown in Figure 1. Figure 5A is a diagram illustrating an example of a method for manufacturing the optical film shown in Figure 1. Figure 5B is a diagram illustrating an example of a method for manufacturing the optical film shown in Figure 1. Figure 5C is a diagram illustrating an example of a method for manufacturing the optical film shown in Figure 1. Figure 5D is a diagram illustrating an example of a method for manufacturing the optical film shown in Figure 1. Figure 6A is a diagram illustrating an example of a method for manufacturing the optical film shown in Figure 1. Figure 6B is a diagram illustrating an example of a method for manufacturing the optical film shown in Figure 1. Figure 7A is a plan view of the optical film shown in Figure 1. Figure 7B is an enlarged view showing a portion of the optical film shown in Figure 7A. Figure 7C is an enlarged view showing another portion of the optical film shown in Figure 7A. Figure 8 is a cross-sectional view showing an example of a display device including the optical film shown in Figure 1. Figure 9 is a diagram illustrating the shape of a mold used in the production of the optical film according to the embodiment, and is an enlarged cross-sectional view of a portion of the mold.

[0009] One embodiment of the present disclosure relates to the following <1> to <13>.

[0010] <1> An optical film having a first surface and a second surface facing each other in a first direction, comprising, in order from the second surface toward the first surface, a substrate, an optical functional layer, and a surface layer, wherein the optical functional layer includes a light absorbing portion and a light transmitting portion, the light absorbing portion and the light transmitting portion are arranged alternately along a second direction perpendicular to the first direction, and the optical film is resistant to bending resistance testing using a cylindrical mandrel with a diameter of 12 mm.

[0011] <2> The optical film described in <1>, which, after being stored at 25°C for four months, is resistant to bending tests using a cylindrical mandrel with a diameter of 12 mm.

[0012] <3> The optical film according to <1> or <2>, wherein the area ratio of the light-absorbing portion in a cross-section of the optical functional layer along the first and second directions is 30% or more.

[0013] <4> The optical film according to <1> to <3>, wherein the light-absorbing portion comprises a base resin and light-absorbing particles held in the base resin.

[0014] <5> The optical film according to <4>, wherein the base resin contains an epoxy oligomer, and the epoxy oligomer content in the base resin is 6% or less.

[0015] <6> The optical film according to <4> or <5>, wherein the refractive index of the light-transmitting portion is higher than that of the base resin, and the light-absorbing portion has a shape that tapers from the first surface to the second surface.

[0016] <7> The surface layer is an optical film according to any one of <1> to <6> that constitutes the first surface including a matte surface.

[0017] <8> The optical film according to any one of <1> to <7>, wherein the light-absorbing portion and the light-transmitting portion extend linearly along a third direction perpendicular to the first direction and the second direction.

[0018] <9> The optical film according to any one of <1> to <8>, wherein the indentation hardness of the light-absorbing portion is 50 MPa or less.

[0019] <10> A film article comprising multiple optical films as described in any of <1> to <9>.

[0020] <11> The film article described in <10>, which is wound around a winding axis.

[0021] <12> A surface light source device comprising an optical film as described in any of <1> to <9>.

[0022] <13> A display device equipped with the surface light source device described in <12>.

[0023] An embodiment of this disclosure will be described below with reference to the drawings. In the drawings attached to this specification, the scale and aspect ratios have been appropriately changed and exaggerated from those of the actual object for the sake of ease of understanding. Some components shown in some drawings may be omitted in other drawings. The scale and aspect ratios may differ between drawings. In cross-sectional views, hatching may be omitted for the sake of ease of understanding.

[0024] In this specification, terms such as "parallel," "orthogonal," and "identical," as well as values ​​of length and angle, which specify shapes, geometric conditions, and their degrees, shall not be limited to their strict meanings, but shall be interpreted to include a range that can be expected to function similarly.

[0025] In this specification, terms such as "sheet," "film," and "plate" are not distinguished from each other solely on the basis of differences in name. For example, "optical film" is a concept that includes components that may also be called optical plates or optical sheets, and therefore, "optical film" cannot be distinguished from components called "optical sheets," etc., solely on the basis of differences in name.

[0026] In this specification, the normal direction of a film-like (sheet-like, plate-like) member refers to the direction parallel to the normal or perpendicular to the film surface (sheet surface, plate surface) of the film-like (sheet-like, plate-like) member in question. The "film surface (sheet surface, plate surface)" refers to the surface that coincides with the film-like (sheet-like, plate-like) member in question when viewed as a whole and in a broad sense.

[0027] To clarify the directional relationships between drawings, some drawings use arrows with common symbols to indicate a common first direction D1, second direction D2, and third direction D3. The tip of the arrow represents the first side of each direction. The opposite side of the arrow represents the second side of each direction. Arrows pointing from the drawing plane toward the viewer, along the direction perpendicular to the drawing plane, are indicated by a symbol of a dot inside a circle, as shown in Figure 1, for example.

[0028] In this specification, multiple candidate upper limits and multiple candidate lower limits for a numerical range may be described in separate sentences. In such descriptions, the numerical range may be constructed by combining any one candidate upper limit and any one candidate lower limit. As an example, consider the description, "Parameter B may be A1 or greater, A2 or greater, A3 or greater. Parameter B may be A4 or less, A5 or less, or A6 or less." In this example, the numerical range of parameter B may be A1 or greater and A4 or less, A1 or greater and A5 or less, A1 or greater and A6 or less, A2 or greater and A4 or less, A2 or greater and A5 or less, A2 or greater and A6 or less, A3 or greater and A4 or less, A3 or greater and A5 or less, or A3 or greater and A6 or less.

[0029] Figure 1 is a schematic cross-sectional view showing the layer structure of the optical film 10 according to this embodiment. The optical film 10 includes a first surface 10a and a second surface 10b facing a first direction D1. The optical film 10 includes a substrate 11, an optical functional layer 12, and a first surface layer 13, in the order from the second surface 10b toward the first surface 10a.

[0030] As shown in the illustrated example, the substrate 11 and the optical functional layer 12 may be in contact with each other. The substrate 11 and the optical functional layer 12 may be in contact with each other and bonded together. The first surface layer 13 and the optical functional layer 12 may be in contact with each other. The first surface layer 13 and the optical functional layer 12 may be in contact with each other and bonded together. The first surface layer 13 covers the optical functional layer 12 from the side opposite to the substrate 11. The first surface layer 13 covers the optical functional layer 12 from the first side in the first direction D1. As shown in Figure 1, the first surface layer 13 may constitute the first surface 10a. The optical functional layer 12 is located between the substrate 11 and the first surface layer 13. In the illustrated example, the first direction D1 is the lamination direction of the substrate 11, the optical functional layer 12, and the first surface layer 13. The substrate 11, the optical functional layer 12, and the first surface layer 13 are located in this order in the first direction D1 and are adjacent to each other.

[0031] As shown in the specific example in Figure 1, the optical film 10 may further include a second surface layer 14. The second surface layer 14 and the substrate 11 may be in contact with each other. The second surface layer 14 and the substrate 11 may be in contact with each other and bonded together. The second surface layer 14 covers the substrate 11 from the side opposite to the optical functional layer 12. The second surface layer 14 covers the substrate 11 from the second side in the first direction. The substrate 11 is located between the optical functional layer 12 and the second surface layer 14. As shown in Figure 1, the second surface layer 14 constitutes the second surface 10b. In the illustrated example, the first direction D1 is the lamination direction of the second surface layer 14, the substrate 11, the optical functional layer 12, and the first surface layer 13. The second surface layer 14, the substrate 11, the optical functional layer 12, and the first surface layer 13 are located in this order in the first direction D1 and are adjacent to each other.

[0032] As shown in Figure 1, the optical film 10 may extend in a direction perpendicular to the first direction D1. The illustrated optical film 10 may also extend in the second direction D2 and the third direction D3. In the illustrated example, the first direction D1 is perpendicular to the second direction D2 and also perpendicular to the third direction D3. In the illustrated example, the optical film 10 is spread on a plane. Unlike the illustrated example, the optical film 10 may also extend on a curved surface.

[0033] The following describes in detail each layer included in the optical film 10 according to this embodiment.

[0034] The base material 11 is made of resin, glass, or the like. The base material 11 may be a film mainly composed of polycarbonate, triacetylcellulose (TAC), polyethylene terephthalate (PET), polyolifin, polyacrylate, or polyamide. The main component refers to the component that is present in the largest quantity among the multiple components that make up a substance. The main component may also be a component that is present in a proportion of 50% or more of the total components of a substance.

[0035] The thickness of the substrate 11 may be 60 μm or more and 400 μm or less, 150 μm or more and 350 μm or less, or 200 μm or more and 300 μm or less. The refractive index of the substrate 11 is, for example, 1.46 or more and 1.67 or less.

[0036] The optical functional layer 12 includes a light-receiving surface 121 and a light-emitting surface 122. The light-receiving surface 121 and the light-emitting surface 122 face each other in a first direction D1. As shown in Figure 1, the optical functional layer 12 may be in contact with the substrate 11 at the light-emitting surface 122. The optical functional layer 12 may be in contact with the first surface layer 13 at the light-receiving surface 121. The light-receiving surface 121 is located between the first surface 10a and the light-emitting surface 122 in the first direction D1. The light-emitting surface 122 is located between the light-receiving surface 121 and the second surface 10b in the first direction D1.

[0037] The optical functional layer 12 includes a light-absorbing portion 12a and a light-transmitting portion 12b. The optical functional layer 12 functions as a louver layer that controls the viewing angle. As shown in the specific examples in Figures 1 and 2, the light-absorbing portion 12a and the light-transmitting portion 12b are arranged alternately in a second direction D2 perpendicular to a first direction D1. The light-absorbing portion 12a and the light-transmitting portion 12b may extend linearly along a third direction D3 perpendicular to the first direction D1 and the second direction D2. As another example, the light-absorbing portion 12a and the light-transmitting portion 12b may be arranged alternately in both the second direction D2 and the third direction D3.

[0038] In the cross-section of the optical functional layer 12 along the first direction D1 and the second direction D2, the area ratio of the light-absorbing portion 12a may be 30% or more, 35% or more, or 40% or more. By setting a lower limit on the area ratio of the light-absorbing portion 12a, the viewing angle can be narrowed.

[0039] In the cross-section of the optical functional layer 12 along the first direction D1 and the second direction D2, the area ratio of the light absorbing portion 12a may be 50% or less, or 45% or less. By setting an upper limit on the area ratio of the light absorbing portion 12a, it is possible to suppress the darkening of the image light.

[0040] The area ratio of the light-absorbing portion 12a is the ratio of the area of ​​the light-absorbing portion 12a to the total area of ​​the light-absorbing portion 12a and the light-transmitting portion 12b, measured in a cross-section along the first direction D1 and the second direction D2 of the optical functional layer 12. The area ratio of the light-absorbing portion 12a is expressed as a percentage. The unit of the area ratio of the light-absorbing portion 12a is %.

[0041] The light absorption part 12a may have a tapered shape toward either the first side or the second side in the first direction D1. As shown in FIG. 1, the light absorption part 12a may have a tapered shape from the light incident surface 121 toward the light emitting surface 122. The light transmission part 12b may have a tapered shape from the second surface 10b toward the first surface 10a. The light transmission part 12b may have a tapered shape from the light emitting surface 122 toward the light incident surface 121. However, the cross-sectional shapes of the light absorption part 12a and the light transmission part 12b can adopt various shapes according to the required functions, and are not particularly limited. For example, they may be rectangular.

[0042] The light absorption part 12a may be exposed to the outside of the optical functional layer 12 on the light incident surface 121 side and may constitute a part of the light incident surface 121. In other words, the light absorption part 12a may be exposed toward the first surface layer 13 on the light incident surface 121 side of the optical functional layer 12 and may constitute a part of the light incident surface 121.

[0043] The light absorption part 12a may include a base resin 12d and light absorption particles 12e. The base resin 12d is a binder resin of the light absorption part 12a. The light absorption particles 12e are held by the base resin 12d. As the light absorption particles 12e, for example, acrylic beads containing carbon black can be used. Note that the light absorption part 12a may be a material in which, for example, a black filler is included in the binder resin, and its composition is not particularly limited.

[0044] The material constituting the base resin 12d in the light absorption part 12a is not particularly limited. The base resin 12d may include a cured resin. The cured resin is a cured product of a curable resin composition. The curable resin composition may be a thermosetting resin composition. The curable resin composition may also be a cured product of an ionizing radiation curable resin composition. The ionizing radiation curable resin composition may be an ultraviolet curable resin composition or an electron beam curable resin composition. The base resin 12d may include a solvent-drying type resin. The solvent-drying type resin is a resin that becomes a film by simply drying the solvent added to adjust the solid content during coating. The base resin 12d may include a mixture of a cured resin and a solvent-drying type resin.

[0045] The base resin 12d may contain an epoxy oligomer. In this case, the content of the epoxy oligomer in the base resin 12d may be 6% or less, may be 4% or less, or may be 2% or less. When the content of the epoxy oligomer in the base resin 12d is 6% or less, the optical film 10 has sufficient flexural resistance and can effectively suppress the occurrence of cracks. The content of the epoxy oligomer in the base resin 12d can be measured, for example, with a high-speed MAS measuring device. Note that the content of the epoxy oligomer in the base resin 12d does not change between before and after curing of the base resin 12d.

[0046] The refractive index of the base resin 12d in the light absorption part 12a may be 1.47 or more and 1.65 or less, or may be 1.49 or more and 1.57 or less. By setting the refractive index of the base resin 12d within this range, the refractive index difference between the base resin 12d and the light transmission part 12b can be reduced, and interfacial reflection between the light absorption part 12a and the light transmission part 12b can be suppressed. By suppressing the interfacial reflection between the light absorption part 12a and the light transmission part 12b, the light incident on the light absorption part 12a can be efficiently absorbed.

[0047] The tensile elastic modulus of the light absorption part 12a may be 70 MPa or less, may be 60 MPa or less, or may be 50 MPa or less. By setting an upper limit for the tensile elastic modulus of the light absorption part 12a, the optical film 10 has sufficient flexural resistance and can suppress the occurrence of cracks. The lower limit of the tensile elastic modulus of the light absorption part 12a is not particularly set. The tensile elastic modulus of the light absorption part 12a may be 1 MPa or more.

[0048] The elongation at break of the light absorption part 12a may be 30% or more, may be 35% or more, or may be 40% or more. By setting a lower limit for the elongation at break of the light absorption part 12a, the optical film 10 has sufficient flexural resistance and can suppress the occurrence of cracks. The upper limit of the elongation at break of the light absorption part 12a is not particularly set. The elongation at break of the light absorption part 12a may be 100% or less.

[0049] The tensile modulus and elongation at break (tensile fracture strain, nominal tensile fracture strain) of the light-absorbing portion 12a are measured according to the test method in accordance with JIS K 7127:1999. The test is performed on a Type 2 sample. The sample is prepared as follows: A resin composition containing light-absorbing particles 12e is sandwiched between PET films and laminated, and then cured. The laminated resin piece is cut into 10 mm x 70 mm pieces to prepare the sample. The thickness of the sample is 30 μm.

[0050] Clamp both ends of the short side of the sample. The distance between the clamps should be 50 mm. Pull the sample at a test speed of 10 mm / min until it breaks. The elastic modulus obtained when the sample is pulled is defined as the tensile modulus. The elongation at which the sample breaks is defined as the elongation at break. The tensile modulus and elongation at break are the arithmetic mean of the measured values ​​of five samples.

[0051] The test environment will be set to a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. The samples to be evaluated will be placed in the test environment for 16 hours before the start of the test.

[0052] The indentation hardness of the light-absorbing portion 12a may be 70 MPa or less, 60 MPa or less, 50 MPa or less, 40 MPa or less, 30 MPa or less, 20 MPa or less, or 10 MPa or less. By having an indentation hardness of 70 MPa or less for the light-absorbing portion 12a, the optical film 10 has sufficient flexibility and can effectively suppress the occurrence of cracks. Preferably, the indentation hardness of the light-absorbing portion 12a is 50 MPa or less.

[0053] The indentation hardness of the light-absorbing portion 12a is measured by the nanoindentation method. The nanoindentation method is a method for measuring hardness based on a load-displacement curve. In the nanoindentation method, the load-displacement curve is obtained by loading and unloading the object to be evaluated using an indenter. The load-displacement curve shows the relationship between the indentation load and the indentation depth. The nanoindentation method allows for the evaluation of hardness in minute areas.

[0054] To measure the indentation hardness of the light-absorbing portion 12a in the optical film 10 in cross-section, a test specimen prepared using the optical film to be evaluated is used. First, a sample is cut from the optical film 10 to be evaluated. The size of the sample is 1 mm × 10 mm when observed from the direction normal to the optical film. This sample is embedded in embedding resin. The embedding resin is a cold-curing type epoxy two-component curable resin. The embedding resin is cured by leaving it at room temperature for 24 hours or more to prepare the embedded sample. The embedded sample is cut with a microtome to expose the cross-section of the optical film 10 along the first direction D1, which corresponds to the direction normal to the optical film. At this time, the cross-section is exposed so that it is nearly flat. The indentation hardness of the cross-section of the light-absorbing portion 12a is measured by pressing an indenter into the exposed cross-section of the light-absorbing portion 12a.

[0055] The indentation hardness of the light-absorbing portion 12a is the arithmetic mean of 10 measurements taken at 10 measurement positions on the optical film to be evaluated. The 10 measurement positions are located in a straight line at a pitch of 5 μm.

[0056] The indenter used to measure the indentation hardness in the cross-section of the optical film 10 is a Berkovich indenter, which has a triangular pyramidal shape. The indenter is pressed into the cross-section of the sample that will be evaluated, from a direction perpendicular to the evaluation surface. The increase in the indentation load of the indenter is set to 2.5 μN / second. The indentation time is set to 10 seconds. The indenter is held for 5 seconds when the indentation load reaches 25 μN. After that, the indenter is withdrawn from the evaluation surface to remove the load from the optical film 10. When removing the load, the indenter is moved along a direction perpendicular to the evaluation surface. The decrease in the indentation load of the indenter is set to 2.5 μN / second. The withdrawal time of the indenter is set to 10 seconds.

[0057] The above operation of the indenter yields a load-displacement curve C as shown in Figure 3A. The load-displacement curve C is a graph relating the magnitude of the load applied to the surface under evaluation via the indenter and the indentation depth of the indenter. Figure 3A shows an example of the load-displacement curve C.

[0058] The indentation hardness is determined by the following equation (1) using the maximum load Fmax and the contact projection area Ap: Indentation hardness = Fmax / Ap ... (1) The maximum load Fmax and the contact projection area Ap are obtained by analyzing the load-displacement curve. The maximum load Fmax is the maximum indentation load. The contact projection area Ap is the projected area onto a plane perpendicular to the indentation direction for the region where the indenter and the sample are in contact at the maximum indentation load. The contact projection area Ap is determined by a correction formula created using a standard method for the apparatus with fused silica as a standard sample.

[0059] The light-transmitting portion 12b may contain a material different from the material contained in the light-absorbing portion 12a. The light-transmitting portion 12b may contain the same material as the material contained in the light-absorbing portion 12a. The material constituting the light-transmitting portion 12b is not particularly limited. The light-transmitting portion 12b may contain a cured resin. The cured resin is a cured product of a curable resin composition. The curable resin composition may be a thermosetting resin composition. The curable resin composition may be a cured product of an ionizing radiation curable resin composition. The ionizing radiation curable resin composition may be an ultraviolet curable resin composition or an electron beam curable resin composition. The light-transmitting portion 12b may contain a solvent-drying resin. A solvent-drying resin is a resin that forms a film simply by drying the solvent added to adjust the solid content during coating. The light-transmitting portion 12b may be a mixture of the cured resin and the solvent-drying resin.

[0060] The refractive index of the light-transmitting portion 12b may be between 1.47 and 1.65, or between 1.49 and 1.57. By setting the refractive index of the base resin 12d within this range, the refractive index difference between the base resin 12d and the light-transmitting portion 12b can be reduced, thereby suppressing interfacial reflection between the light-absorbing portion 12a and the light-transmitting portion 12b. By suppressing interfacial reflection between the light-absorbing portion 12a and the light-transmitting portion 12b, light incident on the light-absorbing portion 12a can be absorbed efficiently.

[0061] The refractive index of the light-transmitting portion 12b may be higher than or the same as the refractive index of the base resin 12d of the light-absorbing portion 12a. If the refractive index of the light-transmitting portion 12b is higher than the refractive index of the base resin 12d of the light-absorbing portion 12a, it becomes possible to use optical design that utilizes total internal reflection of light traveling from the light-transmitting portion 12b to the light-absorbing portion 12a, thereby increasing the efficiency of light utilization, for example. Also, if the refractive index of the light-transmitting portion 12b is the same as the refractive index of the base resin 12d of the light-absorbing portion 12a, no total internal reflection or refraction of light occurs. For this reason, even if the distance from the surface of the display device to the optical film 10 is large, it becomes possible to prevent the occurrence of a double image of transmitted light and total internal reflection or refracted light.

[0062] The pitch of the arrangement of the light-absorbing portion 12a and the light-transmitting portion 12b in the optical functional layer 12 is not particularly limited, but from the viewpoint of effectively exhibiting the function of the louver film, it may be 30 μm or more and 100 μm or less.

[0063] In the example shown in Figure 2, the light-absorbing portion 12a and the light-transmitting portion 12b are located in the same region in the first direction D1. The height D (thickness) of the light-absorbing portion 12a and the light-transmitting portion 12b, that is, the length of the light-absorbing portion 12a and the light-transmitting portion 12b along the first direction D1, are the same. The height D (thickness) of the light-absorbing portion 12a and the light-transmitting portion 12b, that is, the length of the light-absorbing portion 12a along the first direction D1, may be 60 μm or more and 150 μm or less.

[0064] The optical functional layer 12 may include a light-absorbing portion 12a and a light-transmitting portion 12b, as well as a land portion 12c facing the first direction D1. The land portion 12c is in the form of a film. The land portion 12c may support a plurality of light-absorbing portions 12a and a plurality of light-transmitting portions 12b. The land portion 12c may be integrally molded with the light-transmitting portion 12b. The land portion 12c may be connected to the light-transmitting portion 12b without a joint. The thickness of the land portion 12c may be 10 μm or more and 50 μm or less.

[0065] The first surface layer 13 covers the optical functional layer 12 from the light-receiving surface 121 side. The first surface layer 13 protects the optical functional layer 12. The thickness of the first surface layer 13 may be 5 μm or more and 50 μm or less. The refractive index of the first surface layer 13 may be 1.47 or more and 1.65 or less.

[0066] The material of the first surface layer 13 is not particularly limited. The first surface layer 13 may contain a cured resin product. The cured resin product is a cured product of a curable resin composition. The curable resin composition may be a thermosetting resin composition. The curable resin composition may also be a cured product of an ionizing radiation curable resin composition. The ionizing radiation curable resin composition may be an ultraviolet curable resin composition or an electron beam curable resin composition. The first surface layer 13 may contain a solvent-drying resin. A solvent-drying resin is a resin that forms a film simply by drying the solvent added to adjust the solid content during coating. The first surface layer 13 may contain a mixture of a cured resin product and a solvent-drying resin.

[0067] When the optical film 10 is incorporated into the surface light source device 70, it is assumed that the first surface 10a may come into surface contact with other optical components. When the optical film 10 comes into surface contact with other optical components on the first surface 10a, appearance defects such as interference fringes may occur. From the viewpoint of suppressing the occurrence of appearance defects, the first surface 10a may include a matte surface. A matte surface is a rough surface.

[0068] In the illustrated example, the first surface layer 13 constitutes the first surface 10a of the optical film 10. The first surface layer 13 may include the first surface 10a. The first surface layer 13 may constitute the first surface 10a including a matte surface. That is, the first surface layer 13 may be formed as a matte layer.

[0069] The second surface layer 14 is provided to protect the substrate 11. The thickness of the second surface layer 14 may be 5 μm or more and 50 μm or less. The refractive index of the second surface layer 14 may be 1.47 or more and 1.65 or less.

[0070] The material of the second surface layer 14 is not particularly limited. The second surface layer 14 may contain a cured resin product. The cured resin product is a cured product of a curable resin composition. The curable resin composition may be a thermosetting resin composition. The curable resin composition may also be a cured product of an ionizing radiation curable resin composition. The ionizing radiation curable resin composition may be an ultraviolet curable resin composition or an electron beam curable resin composition. The second surface layer 14 may contain a solvent-drying resin. A solvent-drying resin is a resin that forms a film simply by drying the solvent added to adjust the solid content during coating. The second surface layer 14 may contain a mixture of the cured resin product and the solvent-drying resin.

[0071] The second surface layer 14 may contain the same material as the first surface layer 13. In this example, the difference between the coefficient of thermal expansion of the second surface layer 14 and the coefficient of thermal expansion of the first surface layer 13 can be reduced. By reducing the difference between the coefficient of thermal expansion of the second surface layer 14 and the coefficient of thermal expansion of the first surface layer 13, defects such as curling in the optical film 10 can be suppressed. Manufacturing stress can also be reduced by manufacturing the first surface layer 13 and the second surface layer 14 from the same material. The second surface layer 14 may contain a different material than the material contained in the first surface layer 13.

[0072] Next, the flexibility of the optical film 10 will be described. The optical film 10 according to this embodiment is provided with the flexibility described below.

[0073] The optical film 10 is resistant to a flexural resistance test using a cylindrical mandrel with a diameter of 12 mm. In this case, the optical film 10 may also be resistant to a flexural resistance test using a cylindrical mandrel with a diameter of 12 mm after being stored at 25°C for four months. The inventors confirmed that the optical film 10 manufactured by the manufacturing method described later gradually decreased in flexural resistance from immediately after manufacture until a certain period of time had elapsed. Furthermore, the inventors confirmed that the decrease in flexural resistance stopped after four months had elapsed in an environment of 25°C from immediately after manufacture. The flexural resistance of the optical film 10 after four months of storage at 25°C is the flexural resistance evaluated after four months of elapsed in an environment of 25°C from immediately after manufacture, and is generally the lowest flexural resistance of the subject of evaluation. The inventors confirmed that an optical film 10 that withstands a bending resistance test using a 12 mm diameter cylindrical mandrel after being stored at 25°C for four months suppresses the occurrence of cracks in the optical film 10 when it is cut from the film article (long optical film) 100 described later.

[0074] The flexural resistance test using the cylindrical mandrel method is performed as follows:

[0075] A sample measuring 100 mm x 50 mm is cut from the optical film to be evaluated. The pair of sides of the sample, each 50 mm long, are parallel to the third direction D3 of the optical film 10.

[0076] A 180° bending test will be performed using a Type 1 test apparatus as specified in "6.2.1." of JIS K 5600-1:1999. As shown in Figure 3B, the sample will be mounted on the test apparatus so that the second surface 10b is in contact with the mandrel 300. The bending of the sample using the test apparatus will be performed over 2 seconds. The mandrel 300 will be made of stainless steel with a diameter of 12 mm.

[0077] After bending is complete, check the sample surface for defects such as scratches or cracks without removing the sample from the test apparatus. Observe the sample surface under indoor lighting. The observation distance should be approximately 30 cm. The illuminance on the sample surface should be between 800 Lx and 1200 Lx. Check for defects visually or using a 10x magnifying glass.

[0078] Three samples are cut from the optical film to be evaluated. If no defects are found in two or more samples, the film is evaluated as having resistance to the bending resistance test.

[0079] The test environment will be set to a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. Samples cut from the optical film to be evaluated will be placed in the test environment for 16 hours before the start of the test.

[0080] Other conditions for conducting the flexural resistance test using a 12 mm diameter cylindrical mandrel shall conform to JIS K 5600-5-1:1999.

[0081] Furthermore, JIS K 5600-5-1:1999 stipulates that the diameter of the mandrel 300 should be reduced until a defect occurs, and the smallest mandrel diameter that is judged to be resistant to the bending resistance test should be identified. Diameters of mandrel 300 smaller than the 12 mm diameter specified in JIS K 5600-5-1:1999 are specified as 10 mm, 8 mm, 6 mm, 5 mm, 4 mm, 3 mm, and 2 mm. The optical film 10 may, for example, withstand a flexural resistance test using a cylindrical mandrel with a diameter of 10 mm, or a cylindrical mandrel with a diameter of 8 mm, or a cylindrical mandrel with a diameter of 6 mm, or a cylindrical mandrel with a diameter of 5 mm, or a cylindrical mandrel with a diameter of 4 mm, or a cylindrical mandrel with a diameter of 3 mm, or a cylindrical mandrel with a diameter of 2 mm, after being stored at 25°C for 4 months.

[0082] The optical film 10 may withstand a bending resistance test using a cylindrical mandrel with a diameter of 10 mm after being stored at 25°C for one day, or it may withstand a bending resistance test using a cylindrical mandrel with a diameter of 8 mm, or it may withstand a bending resistance test using a cylindrical mandrel with a diameter of 6 mm, or it may withstand a bending resistance test using a cylindrical mandrel with a diameter of 5 mm, or it may withstand a bending resistance test using a cylindrical mandrel with a diameter of 4 mm, or it may withstand a bending resistance test using a cylindrical mandrel with a diameter of 3 mm, or it may withstand a bending resistance test using a cylindrical mandrel with a diameter of 2 mm. The inventors confirmed that the optical film 10 withstands a bending resistance test using a cylindrical mandrel with a diameter of 12 mm after being stored at 25°C for one day was effective in suppressing the occurrence of cracks in the optical film 10 when cutting from a long optical film (film article) 100, as described later.

[0083] Next, the method for manufacturing the optical film 10 will be described with reference to Figures 4A to 4D, 5A to 5D, 6A, and 6B.

[0084] In the example described here, a film article (a long optical film) 100 (see Figure 6A) containing a base material 11 and an optical functional layer 12 is first manufactured. The film article 100 includes a plurality of optical films 10 before cutting. The optical films 10 are obtained by cutting them from the film article 100. As shown in Figure 6A, the film article 100 may be wound around a winding axis.

[0085] First, as shown in Figure 4A, a light-transmitting material layer 12bR is provided on the substrate 11. The light-transmitting material layer 12bR is a coating film of, for example, a curable resin composition before curing. The light-transmitting material layer 12bR is obtained by continuously coating the curable resin composition onto the substrate 11, which is being conveyed by a roll (not shown). In this example, a second surface layer 14 is already provided on the substrate 11, but the timing of the formation of the second surface layer 14 is not particularly limited.

[0086] Next, as shown in Figure 4B, voids 15 for filling the light-absorbing portion 12a are formed in the light-transmitting portion material layer 12bR using a mold. Specifically, in the light-transmitting portion material layer 12bR having a pair of main surfaces, a plurality of voids 15 are formed in a second direction D2 parallel to each of the main surfaces, indenting from one main surface toward the other. The voids 15 may be formed using a roll mold. Then, as the light-transmitting portion material layer 12bR hardens, the light-transmitting portion 12b is formed between adjacent voids 15.

[0087] Next, as shown in Figure 4C, a light-absorbing material layer 12aR is provided so as to cover the multiple light-transmitting portions 12b and the void 15. Here, the light-absorbing material layer 12aR is filled into the void 15. The light-absorbing material layer 12aR is formed from a material that includes, for example, a curable resin composition before curing as a base resin, and also contains light-absorbing particles 12e.

[0088] Next, as shown in Figure 4D, the light-absorbing material layer 12aR is scraped off by the squeegee 120 so that the light-absorbing material layer 12aR fills the void 15 and any excess light-absorbing material layer 12aR is removed. Then, as the light-absorbing material layer 12aR hardens, the light-absorbing portion 12a is formed as shown in Figure 5A. Thus, the optical functional layer 12 is formed.

[0089] Next, as shown in Figure 5B, a surface layer material layer 13R is provided so as to cover the light-transmitting portion 12b and the light-absorbing portion 12a. Then, the surface layer material layer 13R is cured. At this point, the surface layer material layer 13R is in a semi-cured state, not completely cured.

[0090] Next, as shown in Figure 5C, a laminate consisting of a base material 11, a second surface layer 14, an optical functional layer 12, and a surface layer material layer 13R is passed between a pair of embossing rollers 140, 140. Here, the surface of one of the pair of embossing rollers 140, 140 is matte with fine irregularities, and this surface comes into contact with the first surface layer 13 to give the first surface layer 13 a matte finish, in other words, a textured or embossed finish. As a result, as shown in Figure 5D, fine irregularities are formed on the surface of the surface layer material layer 13R, and the first surface layer 13 is formed. By completely curing the first surface layer 13, a film article 100 is manufactured. The longitudinal direction of the manufactured film article 100 may be parallel to the third direction D3, or it may be inclined with respect to the third direction D3.

[0091] The manufactured film article 100 is wound around the winding axis A to form a winding body 101. Then, as shown in Figure 6A, the film article 100 is unwound, and for example, a rectangular optical film 10 is cut out by a die 200 (see Figure 6B) along the dashed line in the figure. The directions parallel to the four sides of the rectangular optical film 10 may be different from the second direction D2 and the third direction D3.

[0092] The length of the short side of the cut rectangular optical film 10 may be 30 mm or more, 50 mm or more, 80 mm or more, or 100 mm or more. The length of the short side of the cut rectangular optical film 10 may be 400 mm or less, 300 mm or less, 200 mm or less, or 150 mm or less. The length of the long side of the cut rectangular optical film 10 may be 100 mm or more, 150 mm or more, 200 mm or more, or 250 mm or more. The length of the long side of the cut rectangular optical film 10 may be 600 mm or less, 500 mm or less, 400 mm or less, or 350 mm or less.

[0093] As shown in Figure 6B, the die 200 cuts out the optical film 10 from the first surface 10a toward the second surface 10b.

[0094] The shape of the optical film 10 is not limited to a rectangular shape. For example, as shown in Figure 7A, the optical film 10 may have tab portions 16A and 16B that are divided into very small sections relative to the overall shape. Figure 7B shows a magnified view of tab portion 16A. Figure 7C shows a magnified view of tab portion 16B.

[0095] Incidentally, cracks can occur in optical films during the cutting process using die-cutting. Cracks are particularly likely to occur in optical films with a large proportion of light-absorbing area. Cracks tend to occur at the interface between the light-absorbing and light-transmitting areas. Furthermore, if the optical film has tab sections, stress concentrates in these areas, making them more prone to cracking.

[0096] Cracking is particularly likely to occur in the tab portions 16A and 16B shown in Figures 7B and 7C. In the example shown in Figure 7B, where the light-transmitting portion and the light-absorbing portion extend in the third direction, cracking is likely to occur at the position indicated by the dotted line in Figure 7B. In the example shown in Figure 7C, where the light-transmitting portion and the light-absorbing portion extend in the third direction, cracking is likely to occur at the position indicated by the dotted line in Figure 7C.

[0097] To address these issues, the optical film 10 according to this embodiment is resistant to bending resistance tests using a cylindrical mandrel with a diameter of 12 mm. The optical film 10 gradually hardens from the time of manufacture and stabilizes after 4 months. The inventors confirmed that the optical film 10, which retains sufficient bending resistance even after being stored at 25°C for 4 months, was able to suppress cracking when being cut from the film article 100 by the die 200.

[0098] Furthermore, the bending resistance test using the cylindrical mandrel method can be easily performed. By performing the bending resistance test, the ease with which the optical film 10 breaks can be easily evaluated. By evaluating the bending resistance in advance using the bending resistance test, it is possible to accurately determine whether or not there are cracks in the cut optical film 10.

[0099] Optical films with a large area ratio of light-absorbing portion are generally expected to have excellent viewing angle adjustment capabilities. Therefore, in optical films with a large area ratio of light-absorbing portion, the light absorption function at the light-absorbing portion tends to be considered more important than the reflection function at the interface between the light-absorbing portion and the light-transmitting portion. Consequently, in optical films with a large area ratio of light-absorbing portion, the refractive index difference between the light-absorbing portion and the light-transmitting portion is reduced. Among the widely used materials applied to the light-absorbing portion, materials that can reduce the refractive index difference with the light-transmitting portion tend to have relatively high hardness. Optical films containing a light-absorbing portion with high hardness are expected to have reduced flexibility, and furthermore, it is expected that cracking will easily occur when cutting from the film article due to the reduced flexibility. This estimation is consistent with the actual phenomenon that optical films with a large area ratio of light-absorbing portion are prone to cracking when cutting from the film article. However, this disclosure is not bound by such estimation.

[0100] An example of how to use the optical film 10 will be explained with reference to Figure 8. Figure 8 is a schematic diagram of a display device 1 including the optical film 10. The display device 1 shown in Figure 8 includes a surface light source device 70, a liquid crystal panel 50, and a visibility adjustment sheet 60 in that order. The surface light source device 70 includes a light source 20, a prism sheet 30, a reflective polarization separation sheet 40, and the optical film 10 in that order. In this example, the first surface layer 13 may come into contact with the reflective polarization separation sheet 40, but if the first surface layer 13 is a matte surface, close contact with the reflective polarization separation sheet 40 is avoided.

[0101] The optical film 10 according to this embodiment described above is an optical film having a first surface 10a and a second surface 10b facing a first direction D1, and comprising a base material 11, an optical functional layer 12, and a surface layer 13 in the order from the second surface 10b toward the first surface. The optical functional layer 12 has a light absorbing portion 12a and a light transmitting portion 12b. The light absorbing portion 12a and the light transmitting portion 12b are arranged alternately along a second direction D2 perpendicular to the first direction D1. The optical film 10 is resistant to bending resistance testing using a cylindrical mandrel with a diameter of 12 mm. According to this embodiment, when cutting the optical film 10 from a film article (long optical film), the occurrence of cracks in the optical film 10 can be suppressed.

[0102] In particular, the optical film 10 according to this embodiment withstands a flexural resistance test using a cylindrical mandrel with a diameter of 12 mm after being stored at 25°C for four months from the date of manufacture. According to this embodiment, when cutting the optical film 10 from a film article (long optical film), the occurrence of cracks in the optical film 10 can be suppressed more effectively.

[0103] In one specific example of this embodiment, the area ratio of the light-absorbing portion 12a in the cross-section along the first direction D1 and the second direction D2 of the optical functional layer 12 may be 30% or more. While a larger area ratio of the light-absorbing portion makes the optical film more prone to cracking, as described above, the optical film 10 has sufficient flexibility, so even if the area ratio of the light-absorbing portion 12a is 30% or more, the occurrence of cracks in the optical film 10 can be suppressed.

[0104] In the specific example shown in Figure 2, the light-absorbing portion 12a may include a base resin 12d and light-absorbing particles 12e held in the base resin 12d. The light-absorbing particles 12e absorb the light incident on the light-absorbing portion 12a, thereby suppressing the widespread diffusion of light. Therefore, the optical film 10 can control the viewing angle.

[0105] In one specific example of this embodiment, the refractive index of the light-transmitting portion 12b may be higher than that of the base resin 12d. The light-absorbing portion 12a may have a tapered shape from the first surface 10a to the second surface 10b. By having a refractive index of the light-transmitting portion 12b higher than that of the base resin 12d of the light-absorbing portion 12a, the total internal reflection of light traveling from the light-transmitting portion 12b to the light-absorbing portion 12a can be utilized. Furthermore, by having a tapered shape for the light-absorbing portion 12a, the viewing angle can be controlled by adjusting the cross-sectional shape of the light-absorbing portion 12a.

[0106] In one specific example of this embodiment, the surface layer 13 may constitute a first surface 10a including a matte surface. Therefore, when the optical film 10 is incorporated into the display device, it is prevented from coming into close contact with other optical components.

[0107] In one specific example of this embodiment, the light-absorbing portion 12a and the light-transmitting portion 12b may extend linearly along a third direction D3 that is perpendicular to the first direction D1 and the second direction D2. Therefore, the viewing angle characteristics of the optical film 10 can be controlled depending on its orientation when incorporated into the display device 1.

[0108] This disclosure will be further described in detail by examples. This disclosure is not limited to the following examples.

[0109] <<<1. Preparation of Optical Films>>> Optical films according to Example 1, Example 2, Comparative Example 1, and Comparative Example 2 were prepared using the method described above.

[0110] <<Example 1>> An optical film according to Example 1 was manufactured using the following materials and dimensions.

[0111] A 250 μm thick polycarbonate film (Opcon PC#250KM20D, manufactured by Keiwa Co., Ltd.) was used as the base material.

[0112] The light-transmitting portion and the land portion were integrally molded by curing ultraviolet-curable urethane acrylate. As shown in Figure 9, the mold 400 that forms the void is a roll mold in which projections 401 having a trapezoidal cross-section with an upper base width W1 of 7 μm, a lower base width W2 of 26 μm, a height L of 120 μm, and a slope angle θ of 5.0° are arranged with a pitch P of 39 μm. The projections 401 of the mold 400 form the void. The roll mold has a cylindrical outer shape. The projections 401 are provided on the side surface of the cylindrical outer shape. The projections 401 extend along the circumference on the side surface.

[0113] The land portion had a thickness of 25 μm. The refractive index of both the light-transmitting portion and the land portion was 1.57. The light-transmitting portion had a tapered shape as it moved away from the land portion. The light-transmitting portion extended linearly along the third direction.

[0114] A UV-curable resin composition containing a urethane oligomer, an acrylate monomer, and an initiator was used as the base resin for the light-absorbing portion. The light-absorbing particles were obtained by incorporating carbon black into acrylic beads with an average particle size of 4 μm. The light-absorbing portion was formed by curing the UV-curable resin composition for the base resin containing the light-absorbing particles. The refractive index of the base resin was 1.54. The area ratio of the light-absorbing portion was 43%.

[0115] A UV-curable resin composition was used as the material for the first surface layer. The first surface layer was formed by curing the UV-curable resin composition. The thickness of the first surface layer was 20 μm.

[0116] A UV-curable resin composition was used as the material for the second surface layer. The second surface layer was formed by curing the UV-curable resin composition. The thickness of the second surface layer was 20 μm.

[0117] <<Example 2>> The optical film according to Example 2 differed from that of Example 1 in that the base resin material was different, but otherwise it was the same as that of Example 1.

[0118] As the base resin for the light-absorbing portion, an ultraviolet-curable resin composition containing a urethane oligomer, an epoxy oligomer, an acrylate monomer, and an initiator was used. The epoxy oligomer content in the solids of the ultraviolet-curable resin composition was 4%. The refractive index of the base resin was 1.54, as in Example 1.

[0119] <<Comparative Example 1>> The optical film according to Comparative Example 1 differed from that of Examples 1 and 2 in that the base resin material was different, but was otherwise identical to that of Examples 1 and 2.

[0120] As the base resin for the light-absorbing portion, an ultraviolet-curable resin composition containing a urethane oligomer, an epoxy oligomer, an acrylate monomer, and an initiator was used. The epoxy oligomer content in the solid content of the ultraviolet-curable resin composition was 8%. The refractive index of the base resin was 1.54, as in Examples 1 and 2.

[0121] <<Comparative Example 2>> The optical film in Comparative Example 2 differed from that of Example 1, Example 2, and Comparative Example 1 in that the base resin material was different, but in other respects it was the same as that of Example 1, Example 2, and Comparative Example 1.

[0122] As the base resin for the light-absorbing portion, an ultraviolet-curable resin composition containing a urethane oligomer, an epoxy oligomer, an acrylate monomer, and an initiator was used. The epoxy oligomer content in the solids of the ultraviolet-curable resin composition was 22%. The refractive index of the base resin was 1.54, as in Example 1, Example 2, and Comparative Example 1.

[0123] The content of epoxy oligomers in the solid content of the UV-curable resin compositions in Example 1, Example 2, Comparative Example 1, and Comparative Example 2 is shown in Table 1 below.

[0124]

[0125] <<<2. Measurement and Evaluation>>> Next, the optical films according to the examples and comparative examples were measured and evaluated. The test environment for measurement and evaluation was set to a temperature of 23°C ± 2°C and a relative humidity of 50% ± 5%. Before starting the measurement and evaluation, the target samples were placed in the above-mentioned test environment for 16 hours. In addition, the samples used for measurement and evaluation were visually inspected to ensure that there were no abnormalities such as dust or scratches. The measurement and evaluation results for Example 1, Example 2, Comparative Example 1, and Comparative Example 2 are shown in Tables 2 and 3.

[0126] <<2-1. Flexural Resistance Test using Cylindrical Mandrel Method>> The optical films according to the examples and comparative examples were subjected to flexural resistance tests using the method described above. Mandrels with diameters of 40 mm, 32 mm, 25 mm, 20 mm, 16 mm, 12 mm, 10 mm, 8 mm, 6 mm, 5 mm, 4 mm, and 3 mm were used in the flexural resistance tests. The flexural resistance tests were continued by decreasing the diameter of the mandrel until the flexural resistance of the optical film was ruled out. The smallest mandrel diameter that was judged to be resistant to the flexural resistance test was identified. The flexural resistance tests were performed on optical films stored at 25°C for 1 day after manufacture, optical films stored at 25°C for 1 month after manufacture, optical films stored at 25°C for 2 months after manufacture, optical films stored at 25°C for 3 months after manufacture, optical films stored at 25°C for 4 months after manufacture, and optical films stored at 25°C for 5 months after manufacture.

[0127] The evaluation results of the flexural resistance test after storage at 25°C for 1 day are shown in the "1 day later" column of Table 2. The evaluation results of the flexural resistance test after storage at 25°C for 1 month are shown in the "1 month later" column of Table 2. The evaluation results of the flexural resistance test after storage at 25°C for 2 months are shown in the "2 months later" column of Table 2. The evaluation results of the flexural resistance test after storage at 25°C for 3 months are shown in the "3 months later" column of Table 2. The evaluation results of the flexural resistance test after storage at 25°C for 4 months are shown in the "4 months later" column of Table 2. The evaluation results of the flexural resistance test after storage at 25°C for 5 months are shown in the "5 months later" column of Table 2. The "1 day later," "1 month later," "2 months later," "3 months later," "4 months later," and "5 months later" columns of Table 2 show the smallest mandrel diameter that was judged to be resistant.

[0128] <<2-2. Evaluation of cracking during cutting>> The presence or absence of cracking was evaluated when cutting the optical films according to the examples and comparative examples from the film articles using a die. Twenty 300 mm x 120 mm samples were cut from the optical films according to the examples and comparative examples. The presence or absence of cracks in the cut samples was visually checked. The evaluation results are shown in the "Cracking" column of Table 2. The evaluation criteria were as follows: A: No cracks were found in any of the samples. B: At least one crack was found in one of the samples.

[0129] <<2-3. Tensile Modulus>> The tensile modulus of the light-absorbing portion of the optical films in the examples and comparative examples was measured using the method described above. A precision universal testing machine "Autograph AG-X" manufactured by Shimadzu Corporation was used as the measuring device. The curable resin composition forming the light-absorbing portion was subjected to an integrated light intensity of 1000 mJ / cm². ２ It was hardened using [method]. The measurement results of the tensile modulus are shown in the "Tensile Modulus" column of Table 3.

[0130] <<2-4. Elongation at Break>> The elongation at break of the light-absorbing portion of the optical films in the examples and comparative examples was measured using the method described above. A precision universal testing machine "Autograph AG-X" manufactured by Shimadzu Corporation was used as the measuring device. The curable resin composition forming the light-absorbing portion was cured with an integrated light intensity of 1000 mJ / cm2. The measurement results of the elongation at break are shown in the "Elongation at Break" column of Table 3.

[0131] <<2-5. Indentation Hardness>> The indentation hardness of the light-absorbing portion of the optical films of the examples and comparative examples was measured using the method described above. A 1 mm x 10 mm sample was cut from the optical films of the examples and comparative examples. A Leica UC7 ultramicrotome was used for this. An Ultra-grade diamond knife blade was used. A BRUKER TI-950 TriboIndenter was used as the indentation hardness measuring device. The BRUKER TI-0039 indenter was used to measure the indentation hardness in the cross-section of the light-absorbing portion. The measurement results of the indentation hardness (MPa) in the cross-section of the light-absorbing portion are shown in the "Indentation Hardness" column of Table 3. The indentation hardness values ​​shown in Table 3 are the average values ​​when the indentation hardness was measured three times. Furthermore, the "-" shown in the "Indentation Hardness" column of Table 3 indicates that the indentation hardness was below the measurement limit.

[0132]

[0133]

[0134] As shown in Table 2, the results from the examples and comparative examples confirmed that optical films that withstand the bending resistance test using a 12 mm diameter cylindrical mandrel after 4 months at 25°C from the time of manufacture are less prone to cracking during cutting.

[0135] As shown in Tables 2 and 3, the results from the examples and comparative examples confirmed that optical films with an indentation hardness of 50 MPa or less are less prone to cracking during cutting.

Claims

1. An optical film having a first surface and a second surface facing each other in a first direction, comprising, in order from the second surface toward the first surface, a substrate, an optical functional layer, and a surface layer, wherein the optical functional layer includes a light absorbing portion and a light transmitting portion, the light absorbing portion and the light transmitting portion are arranged alternately along a second direction perpendicular to the first direction, and the optical film is resistant to bending resistance testing using a cylindrical mandrel with a diameter of 12 mm.

2. The optical film according to claim 1, which, after being stored at 25°C for four months, is resistant to a flexural resistance test using a cylindrical mandrel with a diameter of 12 mm.

3. The optical film according to claim 1, wherein the area ratio of the light-absorbing portion in a cross-section of the optical functional layer along the first and second directions is 30% or more.

4. The optical film according to claim 1, wherein the light-absorbing portion comprises a base resin and light-absorbing particles held in the base resin.

5. The optical film according to claim 4, wherein the base resin contains an epoxy oligomer, and the content of the epoxy oligomer in the base resin is 6% or less.

6. The optical film according to claim 4, wherein the refractive index of the light-transmitting portion is higher than that of the base resin, and the light-absorbing portion has a shape that tapers from the first surface to the second surface.

7. The optical film according to claim 1, wherein the surface layer constitutes the first surface including a matte surface.

8. The optical film according to claim 1, wherein the light-absorbing portion and the light-transmitting portion extend linearly along a third direction perpendicular to the first and second directions.

9. The optical film according to claim 1, wherein the indentation hardness of the light-absorbing portion is 50 MPa or less.

10. A film article comprising a plurality of optical films as described in any one of claims 1 to 9.

11. The film article according to claim 10, which is wound around a winding axis.

12. A surface light source device comprising an optical film according to any one of claims 1 to 9.

13. A display device comprising the surface light source device described in claim 12.

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